appveyor.yml in metanorma-acme-1.2.2 vs appveyor.yml in metanorma-acme-1.2.3

@@ -5,9 +5,10 @@
 cache:
   - vendor/bundle
 
 environment:
   matrix:
+    - RUBY_VERSION: 26
     - RUBY_VERSION: 25
     - RUBY_VERSION: 24
     - RUBY_VERSION: _trunk
 
 matrix: